The theologian Paul Tillich characterized existential anxiety[23] as "the state in which a being is aware of its possible nonbeing" and he listed three categories for the nonbeing and resulting anxiety: ontic (fate and death), moral (guilt and condemnation), and spiritual (emptiness and meaninglessness). According to Tillich, the last of these three types of existential anxiety, i.e. spiritual anxiety, is predominant in modern times while the others were predominant in earlier periods. Tillich argues that this anxiety can be accepted as part of the human condition or it can be resisted but with negative consequences. In its pathological form, spiritual anxiety may tend to "drive the person toward the creation of certitude in systems of meaning which are supported by tradition and authority" even though such "undoubted certitude is not built on the rock of reality".[23]

Once you are under enough stress, almost anything can set off a panic attack. Suppose you are under a lot of stress, but still managing. If you add even more stress, your brain will begin to feel under siege. Your body will respond by releasing adrenaline as part of the fight or flight response. That will cause more anxiety, which will create a vicious feedback that will turn into a panic disorder.
The review, conducted by researchers at Cambridge University in England, also found that people with chronic health conditions were more likely to experience anxiety. According to the review, almost 11 percent of people with heart disease in Western countries reported having generalized anxiety disorder (GAD). In addition, 32 percent of those with multiple sclerosis had some kind of anxiety disorder. (3)

Panic attacks are generally brief, lasting less than 10 minutes, although some of the symptoms may persist for a longer time. People who have had one panic attack are at greater risk for having subsequent panic attacks than those who have never experienced a panic attack. When the attacks occur repeatedly, and there is worry about having more episodes, a person is considered to have a condition known as panic disorder.
While the term "test anxiety" refers specifically to students,[29] many workers share the same experience with regard to their career or profession. The fear of failing at a task and being negatively evaluated for failure can have a similarly negative effect on the adult.[30] Management of test anxiety focuses on achieving relaxation and developing mechanisms to manage anxiety.[29]
In Europe about 3% of the population has a panic attack in a given year while in the United States they affect about 11%.[2] They are more common in females than males.[2] They often begin during puberty or early adulthood.[2] Children and older people are less commonly affected.[2] A meta-analysis was conducted on data collected about twin studies and family studies on the link between genes and panic disorder. The researchers also examined the possibility of a link to phobias, obsessive-compulsive disorder (OCD), and generalized anxiety disorder. The researchers used a database called MEDLINE to accumulate their data.[61] The results concluded that the aforementioned disorders have a genetic component and are inherited or passed down through genes. For the non-phobias, the likelihood of inheriting is 30%-40% and for the phobias, it was 50%-60%.[61]
People with panic disorder often worry about when the next attack will happen and actively try to prevent future attacks by avoiding places, situations, or behaviors they associate with panic attacks. Worry about panic attacks, and the effort spent trying to avoid attacks, cause significant problems in various areas of the person’s life, including the development of agoraphobia (see below).